Negotiations to address the threat caused by Iran’s nuclear program are coming down to the wire in Lusanne, Switzerland. Unlike previous negotiating rounds where an extension seemed inevitable, the domestic politics in both Iran and the United States have brought the situation to a head. The talks may slip beyond today’s self-imposed March 31 deadline, since there is no immediate action by outside interests that may sabotage the talks. However, the U.S. Congress returns from recess in mid-April and will then consider legislation that could derail the negotiations. If a deal – or a “framework deal” or “understanding,” depending on the phrase the negotiators choose to use – is struck today or in the coming days, there are several prominent issues that will be hotly debated by politicians, the public, and the press. Here are three to watch:

Is the Breakout Time Sufficient?

Breakout time is the time necessary for Iran to obtain enough highly enriched uranium for one nuclear weapon. The P5+1 is targeting a year breakout time as an acceptable end-state in the negotiations. The purpose is to have the Iranians far enough away from a weapon that it would be too risky for them to ever try to pursue it without the credible possibility of being caught and attacked. Iran’s breakout time has been below one year for a long time now and is currently at only 2-3 months. However, it has been deterred from taking those final fateful steps towards a bomb precisely because of the risk of being caught red handed, and the potential international response. The logic is that with a breakout time five or six times that length, Iran would almost certainly not risk a dash to a weapon.

Some have argued that the parameters under negotiation by the P5+1 will not achieve a one-year breakout time. But given the sophisticated level of analysis and technical modeling the U.S. Department of Energy has invested in this question, analysts should wait to pass judgment until hearing how the Obama Administration presents its technical case.

Perhaps more important than the technical debate is the one about whether one year is sufficient. Michael Hayden, Olli Heinonen, and Ray Takeyh recently argued that because of bureaucratic challenges, the international community would be too slow to respond to Iranian violations and a longer breakout time is needed.

But, measuring a one-year breakout time is based on Iran having enough enriched uranium for one nuclear weapon. In reality no state has ever dashed to only one nuclear weapon. Instead, states break out to a small arsenal of 6-8 bombs so that they have enough weapons to test their capabilities and a minimum credible deterrent. Achieving such an arsenal would likely take Iran significantly longer than one year.

Assuming a one-year breakout time is also based on the premise that Iran goes full bore for a weapon. However, as Hayden, Heinonen, and Takeyh acknowledge, “any cheating by Iran would always be incremental and never egregious.” That type of incremental cheating is likely to lead to a much longer breakout time, giving the international community sufficient time to respond. For the past year an inspections, verification, and enforcement regime has successfully enforced the interim Joint Plan of Action. Indeed, there was even a minor violation when the International Atomic Energy Agency (IAEA) caught Iran experimenting with a next generation IR-5 centrifuge. Responding to – and reversing – this illicit activity did not take months and the U.N. Security Council. Instead, nuclear negotiators confronted Iran with information about the infraction and the activity was quickly stopped in a matter of weeks.

How to Manage the Sunset?

Critics will argue that Iran will wait out the agreement, which will likely sunset in 10-15 years, and then pursue a nuclear weapon. This is a valid concern that needs to be addressed both inside the agreement itself and through other steps that can be taken outside of the agreement to strengthen implementation.

First, it will be important to examine precisely which elements of the agreement expire and which do not. At a minimum Iran will be subjected to the Non-Proliferation Treaty and Additional Protocol requirements in perpetuity. Beyond that, the Administration has indicated that many of the unprecedented inspections measures that Iran will have to agree to will last far beyond 15 years. If this is true, it significantly reduces concerns regarding the expiration of certain elements of the agreement.

It is also necessary when evaluating the sunset provisions to examine the alternatives. Deal expiration in 15 years is certainly not ideal, but none of the other alternatives buy nearly that type of time. As senior defense officials have previously stated, military action would set Iran’s nuclear program back far less than 15 years at a much greater cost. A return to tougher sanctions may bring Iran back to the table at better terms in a couple of years, but much more likely it will just cause the Iranians to double down on their nuclear program as they did in 2005 when the last serious negotiations on Iran’s nuclear program collapsed.

There are also steps that can be taken outside of the agreement to strengthen it. Here Congress can work with the administration and play a useful role by passing legislation after an agreement is signed that: 1) puts in place very clear metrics for defining violations and forces the executive branch to report on them regularly; 2) creates crushing sanctions that would go into effect if Iran violates the agreement; and 3) provides additional funding for the IAEA to enable a truly robust inspections regime.

The Challenges of Sanctions Relief

Providing sanctions relief to Iran under a potential deal will be sharply criticized by those uncomfortable with the prospect of bringing Iran in from the cold. A deal will offer Iran significant sanctions relief in exchange for significant concession on its nuclear program. It will also offer this exchange up front, in perhaps the first few years, to build confidence among the parties and demonstrate their credibility and commitment.

While Iran’s new economic opening will be closed through a re-imposition of sanctions if it cheats, it will be hard to regain the present powerful economic leverage over Iran once several rounds of concessions are made. Reassembling the broad coalition of international economic sanctions pressure on Iran is possible, though will be extraordinarily difficult. It will only occur if Iran egregiously flouts sanctions or reneges on its nuclear concessions — and that this is made abundantly clear to the global community.

As uncomfortable as it will be to cede much of the economic leverage that the United States and its allies hold over Iran through powerful sanctions, doing so—and doing so in the early stages of a deal--is a necessary step to successful nuclear diplomacy. Iran is extremely unlikely to stick with any deal that doesn’t offer such major sanctions relief. A strong deal will include tough enforcement measures, such as the threat to re-impose sanctions or levy new ones in response to cheating, to keep Iran on the right path. Pragmatic and responsible policymakers should dedicate serious additional resources to support these efforts.

Conclusion

Ultimately, when it comes to difficult and historic international negotiations there are no perfect deals and no perfect mechanisms, just pragmatic agreements that achieve the bottom line objectives of both sides. Viewing the negotiations through that prism, it is clear that a nuclear agreement that maintains a one-year breakout time, has provisions that sunset after 10-15 years, and gives up a significant amount of economic leverage with Iran is not ideal. However, it may be far superior to the alternatives. We should see any agreement in this context and withhold final judgment on the adequacy and durability of a deal until we see the fine print.